Low hemoglobin is associated with worse outcomes via larger hematoma volume in intracerebral hemorrhage due to systemic disease

Whether hemoglobin is associated with outcomes of a specific subtype of intracerebral hemorrhage (ICH) is unknown. A total of 4643 patients with ICH from a multicenter cohort were included in the analysis (64.0% male; mean age [SD], 58.3 [15.2] year), of whom 1319 (28.4%) had anemia on admission. The unsupervised consensus cluster method was employed to classify the patients into three clusters. The patients of cluster 3 were characterized by a high frequency of anemia (85.3%) and mainly composed of patients of systemic disease ICH subtype (SD‐ICH; 90.0%) according to the SMASH‐U etiologies. In SD‐ICH, a strong interaction effect was observed between anemia and 3‐month death (adjusted odds ratio [aOR] 4.33, 95% confidence interval [CI] 1.60–11.9, p  = 0.004), and the hemoglobin levels were linearly associated with 3‐month death (aOR 0.75, 95% CI 0.60–0.92; p  = 0.009), which was partially mediated by larger baseline hematoma volume ( p  = 0.008). This study demonstrated a strong linear association between low hemoglobin levels and worse outcomes in SD‐ICH, suggesting that hemoglobin‐elevating therapy might be extensively needed in a specific subtype of ICH.